The present invention pertains to the optical detector art and, more particularly, to a method for testing a multi-section photo-sensitive detector.
Multi-section photo-sensitive detectors find numerous uses. In the tooling art, for example, extensive use is being made of quadrant detectors, i.e. a detector comprised of four individual photo-sensitive sections sharing a common substrate. In precise machining operations, the aligning of machine tables and tools is accomplished by directing a laser beam from a fixed, known point at a target located on the movable object. Each quadrant of the detector passes a current proportional to impinging light. Thus, upon all four quadrants passing the same current, the beam is known to be striking the precise central portion of the detector, thereby establishing alignment.
As will be understood, it is critical for proper operation of such an aligning system that the various quadrants of the detector track one another and that there be minimal cross-talk between quadrants.
One approach to assuring that the photo-detector meets these requirements has involved measuring a series of individual photo-sensitive detector sections and, based on the data, selecting four sections which track. These four sections are then affixed to a common substrate. This approach is expensive and time-consuming.
An alternate approach has been to place an untested integrated quadrant detector in its manufacturing application and check it out at the job site. If the unit does not perform satisfactorily, it is then replaced with another detector until a suitable one is found. This sort of hit and miss operation is, also, very expensive and time-consuming.
There is a long-felt need in this art, therefore, for a method of testing multi-section, integrated photosensitive detectors, which method assures proper operation of the detector in its intended application and does not require labor-intensive testing.